Ajo, Arizona: New Cornelia Mine

After spending almost two weeks in the Yuma area, we needed to make a move! It’s still a little early to be headed anywhere north so we drove down to Ajo to spend some time catching up with old friends and exploring the desert.

Ajo was founded in 1847 by Tom Childs when he passed through the area en route to mining interests in Mexico. Childs and his party were intrigued by the ore they found. Child’s friend, Peter M. Brady, founded the Arizona Mining & Trading Company which mined surface ores in the area until a ship carrying a load to the smelter in Wales sank off the coast of Patagonia. With transportation costs leading to tiny profit margins, this disaster crippled the small mining company.

New Cornelia Mine from the slopes of Camelback Mountain

In 1900, the Cornelia Copper Company was formed by a group of St. Louis businessmen. The company was unable to find a method to concentrate ores on site—a requirement to compensate for added transportation costs from the remote location of the mine. The company reorganized under the name New Cornelia Mining Company after several disastrous experiments with copper processing.

In 1911, the Calumet and Arizona Mining Company took an option on 70% of the New Cornelia Mining Company stock. John Campbell Greenway headed the subsequent Calumet investigation into the Ajo area copper ore body. More than 25,000′ of drilling showed that there was a substantial copper ore body totaling approximately 30 million tons of ore. Calumet and Greenway exercised their option on the New Cornelia.

Photo NASA via Wikipedia

Calumet located a suitable water source just north of Ajo and was able to develop a practical way to process the ore. A pilot processing plant was completed in 1915 and a rail connection to Gila Bend was completed in 1916. The main processing plant capable of handling 5,000 tons of ore per day was completed in 1917.

In 1917, steam shovels began operation at the New Cornelia, making it the first open pit mine in Arizona. By 1924, the mine had reached lower grade copper-sulfide but continued operation and a concentrator was built to handle the ore.

Calumet and Arizona merged with the Phelps Dodge company in 1931. Under Phelps Dodge, Ajo continued to develop as a company town. The finger print of Phelps Dodge can be seen in the “PD houses” and “PD garages” built to house workers at the New Cornelia. Sometime after taking over, Phelps Dodge built a smelter in Ajo to handle the ore and prepare it for shipment adding additional jobs in Ajo.

In 1982, as a result of declining copper prices, Phelps Dodge laid off most of their workers in Arizona and New Mexico. The New Cornelia reopened and then closed again as a result of a worker strike in 1983. The strike lasted for three years when Phelps Dodge decided it could not afford to add the necessary pollution control measures to the smelter and the mine closed permanently.